Acoustic-vibration coupler



Nov. 11, 1958 J. V. BOUYOUCOS EI'AL ACOUSTIC-VIBRATION COUPLER OriginalFiled June 24, 1954 4 Sheets-Sheet 1 FIG. I

/\\ \\\L A 1 X L ESQ P9 (8 3111111133 INVENTORS JOHN v. BOUYOUCOS BYFREDERICK v. HUNT ATTORNEYS Nov. 11, 1958 J. V. BOUYOUCOS ETALACOUSTIC-VIBRATION COUPLER Original Filed June 24, 1954 4 Sheets-Sheet 2v INVENTORS JOHN V. BOUYOUCOS By FREDERICK V. HUNT ATTORNEYS Nov. 11,1958 J. V. BOUYOUCOS El'AL ACOUSTIC-VIBRATION COUPLER Original FiledJune 24, 1954 FIG. 4

4 Sheets-Sheet 3 INVENTORS JOHN v. aouvoucos FREDERICK v. HUNT WhamATTORNEYS Nov. 11, 1958 J. v. BOUYOUCOS ETAL 2,859,725

ACOUSTIC-VIBRATION COUPLER Original Filed June 24, 1954 4 Sheets-She'et4 INVENTOR. JOHN V. BOUYOUCOS FREDERICK V. HUNT Mam/ AT] "RNEYS UnitedStates Patent ACOUSTIC-VIBRATION COUPLER v John V. Bouyoucos, Cambridgaand Frederick V. Hunt, Belmont, Mass.

20 Claims. (Cl. 116-.137)

The present invention relates to acoustic-vibration couplers, thisapplication being a division of co-pending application, Serial No.439,085, filed June 24, 1954, for Acoustic-Vibration Generator andMethod, issued as United States Letters Patent No. 2,792,804, on May21,, 1957.

In the said co-pending application, there is described an acousticgenerator, oscillator or transmitter that operates by virtue of acousticfeed-back applied to a fluidpressure-actuated valving mechanism. Such avalving mechanism may be made to act periodically to modulate anotherwise uniform flow of a fluid medium and in so doing originatepressure variations, these arising from the alternate fluidaccelerations and decelerations accompanying the modulatory process.These pressure variations may then be transmitted by an acousticfeedback path to the place where they can react in such phase andmagnitude as to control and sustain the valving action, therebyproducing a pulsating flow of the fluid medium for generating acousticvibrations.

As is more fully pointed out hereinafter, there are serious practicallimitations, including considerations of necessary dimensions andefficiency, inherent in using prior-art diaphragms, pistons and similarcoupling devices in conjunction with such acoustic-vibration apparatus.An object of the present invention, accordingly, is to provide a new andimproved coupler for permitting the interchange of acoustic energybetween such generator, oscillator or transmitter apparatus and amedium, such as, for example, a further fluid, disposed external to thegenerator, oscillator or transmitter.

A further object is to provide a novel flexible-walled coupler.

Other and further objects will be .explained hereinafter-and will bemore particularly pointed out in the appended claims.

The invention will now be described in connection with the accompanyingdrawing, Fig. 1 of which is a fragmentary elevation, partly in section,illustrating a coupler constructed and connected in accordance with thepresent invention;

Figs. 2 and 3 are similar views of modifications, Fig. 3 being drawnupon an enlarged scale; and

Figs. 4 and .5 are perspective views, partially broken away,illustrating still further modified coupling devices.

The acoustic pulsations or vibrations generated by an oscillator of theabove-described nature, or by other types.

of fluid-operated acoustic-vibration generators, may, as. described-inthe copending application, be coupled out or conveyed to a. load by aflexible-walled tubular member, illustrated in Fig. l as a helicallywound flexible hose 14. Since" thetdetails of the oscillator 2 with itsvalve mechanism 1 form no part of the present invention and are cPatented 11, 1958 2 I fully set forth in the said copending application,they are but fragmentarily' illustrated in Fig. l. Suflice it to state,for present purposes, that. direct-current fluid flow from a pump 7 isconverted into an acoustically pulsating fluid flow in the oscillatorhousing. 2'. The'outlct 11 of the valve mechanism 1 is shown connectedthrough a pulsation-absorbing filter 13' and tthepump 7 to the lefthandopen end of the helically wound hose 14. iIhe right-hand open end of'thehose 14 is connected to the fluid inlet 8 to complete the hydrauliccircuit. Acoustic vibrations accompanying the pulsating fluid flowthrough the generator 2 will-thus be conducted or propagated along theflexible member 14 as the fluid passes therethrough. The.flexible-walled mernber 14.is preferably constituted of rubber orasimilar flexible material to permit, through flexible movement of itswalls, the trans.- fer of the acoustic pulsations into, for example, anexternaltank 15. The tank 15, may, of course, be much larger than shown,in relation to the. oscillator 2, and. it may contain any desired fluidor other medium into which it is desired to transfer acousticvibrations. Acoustic vibratory energy transmittedbackward through theinlet 8 to the flexible wall hose 14 will thus be dissipated therein bytransfer through the flexible walls ofthe hose 14 into the tank 15.

It is by no means necessary, though, that. the load device 14 bedisposed between the pump 7 and the inlet .8, as shown in Fig. 1. Theload device may, in fact, be connected, as described in the said,copending applica tion, :to any desired portion of the loop 2.. Filters12 and 13 may then be utilized in both the'inlet 8 and outlet 11 toisolate the acoustic circuit of the oscillator 1.2 from the hydraulicsupply pump 7 as illustrated in Fig. 2. The acoustic power generated bythe oscillator of Fig. 2 is shown extracted by a conduit 18 tappedintothe oscillator loop 2 at an intermediate point 19 thereof. The conduit18 leads to the wall 15 bounding a fluid medium 17 and is coupledthrough an aperture 18 in thewall 15 t a longitudinal section offlexible-Walled tubularhosc '14 that. extends longitudinally into thefluid medium 17. The hose 14 is shown terminated or closed at 14' sothat it contains the fluid from theoscillator loop 2. The oscillatoryfluid pressure existing at the point 19 of the loop 2 will give rise toacoustic-vibration pressure waves that travel or propagate through theconduit 18 along the interior of the hose 14,: the flexiblewalls ofwhich will dilate and contract radially in those regions where theinternal pressure is elevated-.01 depressed by the oscillatory pressurewaves transmitted therein. The dilations and contractions of the hose 14give rise, of course, to corresponding radialrnotions of the externalsurfaces of 14, and these motions, in tumwwill generate compressionalacoustic waves in the medium 17 surrounding the hose. 14. .Acousticenergy isthus ,transterredor coupled from the oscillatorgl-Z into themedium 17.

In the case of a flexible-walled tubular hose 14 that is very longcompared to the wavelength of the generated acoustic energy,.the;acoustic-energy radiation pattern of the hose 14 may be quitedirectional and of the'cnd-fire type, having a major lobe thatsubstantially coincides with the longitudinal axis of the straightyhose14. In gen:

eral, the width of the directivity pattern of such-a hose 14 dependsprimarily upon theratio of the velocity of the pressure wave-withinthehose 14to the velocity of free acoustic waves in the medium 17, highdirectivi-ty being achieved when this ratio approaches unity. The

'directivity pattern and the axial rate of acoustic energy transfer fromthe hose 14 to the medium 17 are thus dependent upon the characteristicsof the media both within and without the hose 14 and also upon theproperties of the material from which the hose 14 is fabricated. It isthus possible with the aid of a load 14 of this character to couple highpower from the oscillator 1-2 and to transmit such high power with highdirectivity without resorting to diaphragms or pistons whose physicaldimensions would need to be many times the acoustic wavelength in orderto produce a corresponding directional gain. In addition, the oscillator12 itself may have an outlet 18 that, unlike prior-art diaphragms andpiston sources of acoustic energy, has dimensions that may beconsiderably less, instead of many times, the acoustic-energywavelength.

In the systems of Figs. 1 and 2, as in the other cmbodiments of theinvention hereinafter described, it is to be understood that while aparticular load configuration or use for the energy may be described inconnection with any particular figure, this is illustrative only, andsuch load configuration or use may equally well be adapted to thesystems of the other figures. Typical uses for the acoustic energyinclude, for example, the agitation or processing of fluid and othermedia, and the production of acoustic signals for communication orobject detection. If desired, moreover, a fluid to be processed mayindeed be pumped from the pump 7 through the oscillator 12 itself,serving as the fluid for the oscillator.

We have successfully operated an oscillator of the character illustratedin Figs. 1 and 2, for example, at oscillation frequencies ranging from550 to 700 cycles per second with static fluid pressures from the pump 7of from 20 to 50 lbs. per square inch. The loop 2 was made of coppertubing having a wall thickness of about 0.1 cm., a cross-sectionaldiameter of about 1.5 cm. and a loop-length of about 75 cm. The ratio ofthe length of the loop 2 to the wavelength of the oscillations rangedfrom about 0.3 to about 0.4. The oscillation frequency was, in sometests, below the mechanical resonant frequency of the wave assembly 1,which was about 1000 cycles per second. The fluid employed was water andthe velocity of sound in the water-filled loop 2 as modified by thefinite elasticity of the loop wall was about l.3 cm. per second. Thedirect-current flow power input from the pump 7 was from 4 to 8 watts,and the circulating or reactive acoustic-oscillation power in the loop 2of this particular relatively low-power oscillator was estimated to beseveral watts prior to connection to the flexible-walled coupler hose14. As before indicated, for some purposes, a resonant system is desiredin which case the effective acoustical length of the flexible tubularmember 14 may be any integer multiple of the quarterwavelength of theacoustic-vibration waves; whereas for t other purposes, as previouslyexplained, the flexible member 14 may extend from the oscillator 2 manywavelengths of the acoustic-vibration waves.

In Fig. 3, the flexible-walled coupler 14 is shown cooperating with asomewhat modified oscillator 2, ineluded within the dotted lines 100,being joined thereto by means of flanges 118'. The modified hose 14 ofFig. 3, however, is open at its terminal cap 14', as illustrated at114'. The combined assembly is shown submerged within a fluid medium 17,separated by a bulkhead 15 from the supply pump 7. Pump 7 obtains itshydraulic supply from the medium 17 by means of the inlet 11, anddelivers the fluid through the low-pass acoustic filter 13 to the inlet8 of the oscillator. The fluid passes through multiple orifices 409,later described, and into and through a conduit 118 and the flexiblewalled hose 14, finally to discharge into the medium 17 through theopening 114' in the end cap 14'. By controlling the size of the opening114, the average pressure within conduit 118 and the hose 14 may beelevated above that of the surrounding medium 17. Since the peaknegative pressure variation is limited by the absolute magnitude of theaverage pressure, in this way greater internal pressure variationsaccompanied by increased acoustic energy densities are allowed. Thedetails of operation of this oscillator are set forth in the saidcopending application so that they need not be repeated here. The supplyflow from the pump 7 is modulated at the valve assembly 401 by aperiodic motion of the valve 404, giving rise to variationalaccelerations of the fluid flux from the orifices 409 into the conduit118. This modulatory action upon the flow acts as an equivalent acousticvolume velocity source to generate progressive acoustic-vibration wavesthat travel down the conduit 118 and into the flexible walled hose 14,therein to be dissipated as previously described. The mode of operationof the oscillator of Fig. 3 will not be fundamentally changed if all theenergy of the outward-progressing wave is not completely transferred tothe medium 17 in a single transit through the hose 14, so thatreflection occurs at the termination 114 and a standing wave system isthereby established in the conduits 118 and 14.

While the coupler of the present invention is preferably of tubularform, it may, also, assume other curved surface configurations. Thegenerator, oscillator or transmitter of Fig. 4, for example, isconstructed to employ the radial or extensional motion of the externalsurfaces of a flexible elastic shell 36, as it compresses and expands,to impart acoustic energy stored in the oscillator to the mediumsurrounding the shell 36; or, if desired, other output coupling meansmay be used, as before discussed. The details of the operation of theoscillator of Fig. 4 are described in the said copending application;but, since the shell 36, the inner surface of which bounds the fluidmedium of the oscillator, operates as a coupler for the acousticvibrations that are generated, reptition of the mode of operation may beuseful. Assuming that a steady flow has been established in thehydraulic circuit of Fig. 4, and that the valve mechanism 1 is caused toperform an incremental closure, the fluid flow through the orifice 209is then throttled with the result that a pressure rise is establishedthroughout the fluid contained in the cavity 32. This pressure riseproduces both a compression of the fluid contained within the cavity 32,and an expansion or extension of the flexible shell wall 36 of thesphere, accompanied by a displacement of fluid into the hollow 202 ofthe block 206. An increase in the pressure upon the left-hand face ofthe valve disc 204 is thereby produced, causing the valve disc 204 tomove to the right and away from the valve seat 203, thus increasing thearea of the orifice 209. This, in turn, allows more fluid to dischargethrough the chamber 210 and the outlet 11, reducing the pressure acrossthe orifice 209. Accompanying the reduced pressure associated with thisincreased discharge rate will be an expansion of the fluid within thecavity 32 and a contraction of the shell wall 36, thus releasing fluidfrom the hollow 202 of the block 206 and thereby reducing the pressureon the left-hand face of the valve disc 204 and allowing the orifice 209to close again. The resulting decrease in orifice discharge produces arise in the pressure in the fluid of the cavity 32 again, and so on. Itis thus evident that, as in the case of the system of Fig. 1, pressurefluctuations are fed back through the transmission path provided by themembers 202 and 32, in just such a way as to sustain self-excitation ofthe oscillator. This acoustic oscillation, moreover, will occur at afrequency at which the effective acoustic compliance of the shell wall36 lumped in parallel with the compliance of the fluid contained thereinresonates with the series impedance of the mass of the fluid containedwithin the hollow 202 and the acoustical compliance of the suspension ofthe valve mechanism 1. For the specific oscillator of Fig. 4, thisfrequency must be low enough for the equivalent wavelength of pressurewaves in the fluid enclosed within the shell 36 to be at least as largeor larger than the diameter of the flexible shell 36.

For purposes of providing still another illustration of a somewhatdifferent type of acoustic-energy coupling device, the cantilever-beamvalve-structure oscillator of Fig. 5, which is fully explained in thesaid copending application and need not be further elaborated uponherein, is shown having its pulsating fluid medium bounded by an elasticcylindrical coupler surface or window 40 in the wall of the chamber 300.The motion of this elastic surface in response to pressure variations inthe central region 37, permits acoustic energy to be radiated from theoscillator into a surrounding medium in which the assembly of Fig. 5 maybe immersed.

Further modifications will occur to those skilled in the art and allsuch are considered to fall within the spirit and scope of the inventionas defined in the appended claims.

What is claimed is:

1. In an acoustic generator system in which acoustic vibrations arepropagated within a fluid medium, an acoustic-vibration output couplingdevice comprising a flexiblewalled tubular member connected to receivethe fluid medium, both ends of the tubular member being open to permitpassage therethrough of the fluid medium.

2. In an acoustic generator system in which acoustic vibrations arepropagated within a fluid medium, an acoustic-vibration output couplingdevice comprising a flexible-walled tubular member connected to receivethe fluid medium, the flexible-walled tubular member being helicallywound.

3. In an acoustic system in which acoustic vibrations are propagatedwithin a fluid medium, an acoustic-vibration output coupling device fortransferring acoustic energy from the system to a further medium, thatcomprises a flexible-walled tubular member having an open end forreceiving the fluid medium from the system.

4. In an acoustic system in which acoustic vibrations are propagatedwithin a fluid medium, an acoustic-vibration output coupling device fortransferring acoustic energy from the system to a further medium, thatcomprises a longitudinally extending flexible-walled tubular memberhaving an open end for receiving the fluid medium from the system.

5. In an acoustic system in which acoustic vibrations are propagatedwithin a fluid medium, an acoustic-vibration output coupling device fortransferring acoustic energy from the system to a further medium, thatcomprises a curved flexible-walled tubular member having an open end forreceiving the fluid medium from the system.

6. In an acoustic system in which acoustic vibrations are propagatedwithin a fluid medium, an acoustic-vibration output coupling device fortransferring acoustic energy from the system to a further medium, thatcomprises a helically wound flexible-walled tubular member having anopen end for receiving the fluid medium from the system.

7. In an acoustic system in which acoustic vibrations are propagatedwithin a fluid medium, an acoustic-vibration output coupling device fortransferring acoustic energy from the system to a further medium, thatcomprises a flexible-walled tubular member having an open end forreceiving the fluid medium from the system and of length substantially amultiple of the quarter-wavelength of the acoustic vibrations.

8. In an acoustic system in which acoustic vibrations are propagatedwithin a fluid medium, an acoustic-vibration output coupling device fortransferring acoustic energy from the system to a further medium, thatcomprises a flexible-walled tubular member having an open end forreceiving the fluid medium from the system and of length long comparedto the wavelength of the acoustic vibrations.

9. In an acoustic system in which acoustic vibrations .6 are propagatedwithin a fluid medium, an acoustic-vibration' output coupling 'devicefor transferring acoustic energy from the system to a further medium,that comprises a flexible-walled tubular member having an open end forreceiving the fluid medium from the system and closed at the other end.

10. In an acoustic system in which acoustic vibrations are propagatedwithin a fluid medium, an acoustic-vibration output coupling device fortransferring acoustic energy from the system to a further medium, thatcomprises a flexible-walled tubular member having an open end forreceiving the fluid medium from the system and closed at the other endand of length substantially a multiple of the quarter-wavelength of theacoustic vibrations.

11. In an acoustic system in which acoustic vibrations are propagatedwithin a fluid medium, an acousticvibration output coupling device fortransferring acoustic energy from the system to a further medium, thatcomprises a flexible-walled tubular member having an open end forreceiving the fluid medium from the system and closed at the other endand of length long compared to the wavelength of the acousticvibrations.

12. In an acoustic system in which acoustic vibrations are propagatedwithin a fluid medium, an acousticvibration output coupling device fortransferring acoustic energy from the system to a further medium, thatcomprises a flexible-walled tubular member open at both its ends topermit passage of the fluid therethrough.

13. In an acoustic system in which acoustic vibrations are propagatedwithin a fluid medium, an acoustic-vibration output coupling device fortransferring acoustic energy from the system to a further medium, thatcomprises a flexible-walled tubular member open at both its ends topermit passage of the fluid therethrough and of length substantially amultiple of the half-wavelength of the acoustic vibrations.

14. In an acoustic system in which acoustic vibrations are propagatedwithin a fluid medium, an acoustic-vibration output coupling device fortransferring acoustic energy from the system to a further medium, thatcomprises a flexible-walled tubular member open at both its ends topermit passage of the fluid therethrough and of length long compared tothe wavelength of the acoustic vibrations.

15. In an acoustic system in which acoustic vibrations are propagatedwithin a fluid medium, an acoustic-vibration output coupling device fortransferring acoustic energy from the system to a further medium, thatcomprises a flexible-walled member curved in cross-section and boundingalong its inner surface at least part of the fluid medium.

16. In an acoustic system in which acoustic vibrations are propagatedwithin a fluid medium, an acousticvibration output coupling device fortransferring acoustic energy from the system to a further medium, thatcomprises a flexible substantially cylindrical-wall member boundingalong its inner surface at least part of the fluid medium.

17. In an acoustic system in which acoustic vibrations are propagatedwithin a fluid medium, an acoustic-vibration output coupling device fortransferring acoustic energy from the system to a further medium, thatcomprises a flexible substantially spherical-wall member bounding alongits inner surface at least part of the fluid medium.

18. In an acoustic system in which acoustic vibrations are propagatedwithin an acoustic-vibration transmitter, a flexible-walled tubularacoustic-vibration conducting device connected at one end to thetransmitter to receive the fluid medium therefrom, the tubular deviceextending outward away from the transmitter a distance large compared tothe wavelength of the acoustic vibrations.

19. In an acoustic system in which acoustic vibrations are propagatedwithin an acoustic-vibration transmitter, a flexible-walled tubularacoustic-vibration conducting device connected at one end to thetransmitter to receive the fluid medium therefrom, the tubular deviceextending outward away from the transmitter into a further fluid mediuma distance large compared to the wavelength of the acoustic vibrations,thereby to transmit the acoustic vibrations propagated along the tubulardevice into the further fluid medium.

20. An acoustic system as claimed in claim 19 and 10 in which thetubular walls are constituted of material such that the ratio of thevelocity of the acoustic vibrations within the tubular device to thevelocity of free acoustic vibrations in the further fluid mediumapproaches 5 unity.

References Cited in the tile of this patent UNITED STATES PATENTS2,792,804 Bouyoucos May 21, 1957

